1. Field of the Invention
This invention relates to a Class-II restriction endonuclease which recognizes a specific sequence of seven bases in a double stranded deoxyribonucleic acid (DNA) molecule and cleaves said DNA molecule at specific sites.
2. Description of Related Art
Restriction endonucleases are endonucleases that are capable of recognizing a specific sequence of bases in a DNA molecule and cleaving the DNA strands at specific sites. Many kinds of restriction endonucleases have so far been found. As a result of the progress in molecular genetics and biochemistry, DNA was proven to be the carrier of genetic information, and since then restriction endonucleases have been extensively used for various purposes, such as in the clarification of genetic diseases in gene manipulation.
Among them, class II restriction endonucleases, which can recognize specific DNA sequence and digest the DNA strand specifically within the sequence, are especially important and essentially used in genetic engineering techniques.
More than 300 class II restriction endonucleases have been isolated, however, many DNA sequences having no cognate restriction endonucleases (can not be recognized by any known restriction endonuclease) still remain. Therefore, it has been needed to make effort for discovering novel class II restriction endonucleases having ability to recognize and digest these sequences, so that researchers have more chance to cut their DNA at positions suitable for each experiment.
Moreover, restriction endonucleases with low cutting frequencies are more convenient for structural analyses of high molecular weight DNA such as genome analysis projects of several living things, and the discovery of the class II restriction endonucleases recognizing long DNA sequences more than six bases have been demanded.